Electromagnetic relay



May 14,v 1946. E w oD' 2;400,452

ELECTROMAGNETIC RELAY Original Filed Feb. 26, 1943 INSULATION has fi/ I) INVENTOR. FR EDRIO E. WOOD ATTOR N EY Patented May 14, 1946 UNITED STATES PATENT OFFICE tomatic Electric Laboratories, Inc.,

Chicago,

Ill., a corporation of Delaware Original application February 26, 1943, Serial No.

477,230. Divided and thi 17, 1944, Serial No. 522

3 Claims.

The present invention relates in eneral to electromagnetic devices and, more particularly, to electromagnetic devices of the relay type, and is a division of my prior application Serial No. 477,- 230, filed February 26, 1943.

An electromagnetic device of the relay type conventionally comprises a field structure includ- 5 application February Another object of the invention is to provide in an electromagnetic relay an improved multicontact switch spring arrangement which positively insures electrical contact between each pair of associated contacts carried by the switch springs and which accommodates equalization of the contact pressure between associated contacts.

The objects set forth above are in part realized in accordance with one feature of the present invention by providing an electromagnetic relay which comprises one or more sets of switch springs, each set comprising one or more so called armature springs, which are movable under control of the relay armature, and one of more so called make or break springs, engageable with or disengageable from said movable armature springs under control of said armature, wherein each of the armature springs comprises a relatively long flexible portion and is provided with two spaced-apart and independently flexible portions and a plurality of contacts carried by the flexible portions, and wherein each of the make or break springs comprises a relatively short stiff portion and is provided with two spaced-apart and independently flexible portions and a plurality of contacts carried by the flexible portions, the contacts carried by the flexible portion of the armature spring cooperating with the contacts carried by the flexible portions of the make or break springs. More particularly, each of the break or make springs is formed of' flat metallic stock and is provided with a base end and a free end comprising a relatively short stiff portion to facilitate maximum ease of adjusting the relative position thereof, and a pair of short and very flexible branches which are of unequal cross section and unlike shape to reduce contact-bounce to a minimum, to maintain the cooperating circuit closing contacts clean and clear of dirt or dust particles by wiping such contacts in small arcs in diiierent planes and to equalize the contact pressure between cooperating contacts of armature springs.

Each of the armature springs is formed of flat metallic stock and is provided with a base end and a free end comprising a relatively long flexing portion to facilitate maximum ease of adjusting the pressure of the spring against the armature or cooperating prin and minimum operating power from the relay to move the armature, thereby to effect a change in the relative positions of the contacts on the armature springs with respect to the cooperating contacts of the make or break springs.

The two independently flexible portions provided in the armature spring are formed by an elongated slot provided adjacent the free end thereof and the two flexible portions provided in the make or break spring are for-med by an elongated L-shaped slot provided at the free end thereof. Also, the contacts respectively carried by the flexible portion of the spring are carried thereby at points along the lengths of the flexible portions whereat the flexible portions have a maximum movement with respect to the base portion of the springs, thereby to insure self equalization of contact pressure between the respective engaging contacts when the contacts carried by the flexible portion of the armature springs are respectively forced into engagement with the contacts respectively carried by the short flexible portions of the associated make or break springs.

Furthermore, the means for moving the armature springs comprises an operating member carried by each armature spring adjacent the free end and intermediate the two flexible portions thereof and an arm including the relay armature operating to engage the operating member.

Other features of the present invention will be apparent by reference to the following specification taken in connection with the accompanying drawing, in which Fig. 1 is a side view of an electromagnetic relay constructed and arranged in accordance with the present invention;

Fig. 2 is a right end view of the relay illustrated in Fig. 1;

Fig. 3 is an exploded perspective view of the electromagnetic relay illustrated in Fig. 1;

Fig. 4 is an enlarged sectional view showing the arrangement for pivotally supporting the re lay armature;

Fig. 5 is a plan view of an electromagnetic relay constructed and arranged in accordance with the present invention but modified to accommodate two separate switch spring sets;

Fig. 6 is a right end view of the modified relay iliustrated in Fig. 5.

Referring now more particularly to Figs. 1 to l, inclusive, of the drawing, the electromagnetic relay there shown comprises a field structure including a longitudinally extending core element l2 provided with a winding l3, a substantially L shape magnetic heel piece l4, secured to the core element l2, by means of a screw I0, and a movable magnetic armature l5 pivotally mounted upon the outer end of the heel piece l4 and cooperating with the core element l2.

The switch springs 28, 21, and 28 as disclosed,

comprise a so-called break-make spring combination in which the armature spring 21 is adapted to be moved out of engagement with the cooperating break spring 28 into engagement with the cooperating make spring 28. In order to facilittae maximum ease of adjustment of the relative position of springs 28 and 28 with respect to the armature spring 21, these springs are provided with a relatively short stiif portion extending from the base end thereof, and a pair of very flexible branches 34 and 35. tions 34 and 35 of springs 28 and 28 carry adjacent the free end thereof a pair of metallic contacts.

Although the pair of flexible branch portions of springs 26 and 28 are of unequal cross-section and of unlike shape, they provide, in combination with the associated relatively long, but flexible, armature spring 21, an arrangement which equalizes the contact pressure between cooperating contacts of associated cooperating springs. Since the branch portions 34 and 35 are very flexible, the position to which the stiff portions of these springs are adjusted with respect to the cooperating armature spring 2'l' may be approximate rather than accurate.

The armature spring 21 is provided with a relatively long, flexible portion, as compared with the relatively short, stiff portion of the cooperating make and break springs 26 and 28, to facilitate maximum ease of adjusting the pressure of this spring against the break spring 28, or, if no break spring such as 28 is provided, against the operating projection Ila, whereby minimum operating power is required of the relay to overcome the tension of this spring in order to disengage the armature spring 21 from the cooperating break spring 28 and to move it into engagement with the cooperating make spring 26. In the event no break spring 28 is required, the armature restoring spring 29 may be omitted in which case the bushing 4| on the spring 21 may directly engage the operating projection l'la. More particularly, the armature spring 21 is provided with an elongated longitudinally extending slot 35 formed therein adjacent the free end thereof, which slot provides the armature spring with two spaced apart and independently flexible branches 31 and 38, connected together at the free end thereof by a curved operating portion 39.

The flexible portions 31 and 38 of the armature spring 21 each carry a metallic contact. One pair is provided on, the bottom side of the spring to cooperate respectively with the pair of contacts provided on the top side of the break spring 28; and the other pair is provided on the The flexible portop side of the spring to cooperate respectively with the pair of contacts provided on the bottom side of the make spring 25. Each of the spring contacts is welded to its associated flexible portion of the springs at a point along the length of the flexible portion of the associated spring, whereat the flexible portion has a maximum movement with respect to the base end or relatively stiff body portion of its associated spring, thereby to insure self-equalization of the contact pressure between the respective engaging contacts, either when the contacts of the armature spring 21 and the contacts of the break spring 28 are in engagement, or when the contacts of the armature spring 21 and the contacts of the make spring 28 are in engagement.

In order to facilitate movement of the armature spring 2?, with respect to the associated break and make springs, a substantially cupshaped metallic fixture 48 is securel fastened b welding or the like to the lower surface of the curved operating portion 39 of the armature spring 27. A substantially cylindrical insulating operating element, or bushing 4|, is arranged within the fixture 40 and frictionally secured in place by the side wall thereof, Preferably, one end of the bushing 4| is provided with an inverted irusto-conical section which is inserted into the cup-shaped fixture 40, and then the side wall of the fixture is spun or pressed down into iii-m engagement with the conical side wall of the received section of the bushing 4|. The specific construction and arrangement described above is disclosed in the copencling application of Fredric 13. Wood, Serial No. 459,121, filed September 21, 1942.

The bushing 4| cooperates directly with the armature restoring and restraining spring 29, and contacts on the armature spring 21 are adapted to be urged thereby out of engagement with the cooperating contacts on the break spring 28 into engagement with the cooperating contacts on the make spring 28. More particularly, when the winding l3 is energized, the armature I5 is r0- tated about the pivot pin 20 in a counterclockwise direction as viewed in Fig. 1, thereby to cause the armature hi to be moved from its normal position to its operated position. When this occurs, the pivot pin 26 rotates in the transverse pivot pin receiving slot 2| formed in the bottom side of the clamping plate ls, the adjacent upper surface of the bearing plate Ill serving also as a bearing surface therefor. Also, at this time the operating projection lla, carried by the arm ll of the armature l5, acts upon the armature restoring spring .29 and the bushing 4|, and consequently, upon armature spring 27. Accordingly, the armature spring 27 is flexed, whereby the normally engaged contacts of the associated break spring 23 disengaged, and the normally disengaged contacts oi the associated make spring 26 are engaged b the associated cooperating contacts of the armature spring 21.

It is to be noted that the non-magnetic rivet 22 underlying the operating projection Ila prevents the projection mentioned from sticking to the adjacent surface of the heel piece l4, due to leakage of magnetic flux therebetween.

In order to prevent objectionable play between the pivot pin 29 and the bearing surfaces, comprising the transverse pivot pin receiving slot 2| and the bearing plate l8, when the entire. relay structure is vibrated from an external source, the relatively long flexible restoring spring 29 is lightly tensioned against the upper surface of the operating projection arm Ila. between the point where the bottom surface thereof rests upon the rivet 22 and the point where the arm I! joins the projection Ho. The rivet 22 acts as a fulcl'um, so that pressure applied to the upper surface of the operating projection l'la at a point removed from the fulcrum tends to twist the armature 55, as is clearly shown in a slightly exaggerated form in Fig. 2. Consequently, if there is any play between the pivot pin 20 and the bearing surfaces indicated above, the armature restoring spring automatically takes up the play therebetween and thereby prevents vibration of the armature from an external source, either transverse to the axis of the pivot pin or parallel to the axis of the pivot pin.

In view of the fact that the armature restoring spring 29 applies its pressure to the operating projection iia at a point remote from the pivot pin 26 and also at a point remote from fulcrum considerably less pressure is required to overcome any tendency of the armature I to vibrate from an external source than would be required if the pressure was applied directly to the pivot pin itself. By actual test, it has been found that very small percentage of the pressure required at the pivot pin to prevent vibration of the armature, is required when the pressure is applied to the operating projection Ila at the remote end of the armature !5 in the-manner shown.

It may be well to mention at this time that in the event that the break spring 23 is omitted from the combination of switch spring set 25, the necessity of providing a separate armature restoring spring, such as spring as, is eliminated, because the function of restoring the armature and applying the necessary pressure to the operating projection Ha may then be performed by the armature spring 21.

Referring now to Figs. 5 and 6 of the drawing, there is shown therein an electromagnetic relay, constructed and arranged in accordance with the relay constructure disclosed in Figs. 1 to 4, inclusive, but modified to accommodate two separate switch spring sets. More particularly, the lefthand switch spring set 42 of Fig. 6 i identical to the switch spring set 25, except that the clamping plate 3% and the bearing plate l8 are increased in width to accommodate both the lefthand switch spring set 42 and the right-hand switch spring set 43. Furthermore, the armature of the modified relay is provided with left and right hand armature arms 44 and t5 and associated operating projections 44a and 45a, instead of a single armature arm I! and a single operating projection Ila as is provided in the relay disclosed in Figs. 1 to 4 inclusive. A nonmagnetic rivet 46 is provided, underlying the operating projection 45a, to prevent the armature operating projections 44a and 45a from sticking to the adjacent heel piece and to provide a fulcrum about which the armature tends to twist and take up objectionable play in the same manner as has been previously described.

It is to be noted, however, that the switch spring set 43 does, not include an armature re- Storing and restraining spring such as spring 29. A spring of this type is included, however, in the switch spring set 42 and provides the necessary pressure to the armature in order to automatically take up any play which might occur between the armature pivot pin and its bearing surfaces, and thereby prevents Vibration of the armature from an external source.

Having described the construction and assembly of the relay, the utility and purpose of the invention will be set forth to enable the same to be more fully understood and appreciated.

The short main stifi portion of spring 26 extending from its mounting base may be adjusted to simultaneously position both arms 34 and 35 without individually adjusting the arms 34 and 35 thereby maintaining relative position and equal tension in both arms 34 and 35. The short arms 34 and 35 of spring 26 are flexible with respect to the short main stiff portion to give greater flexing characteristics compared to the sprin as a who-1e. These short flexible spring 34 and 35, however, are relatively stifi when compared to the flexibility of the long armature spring 2?. The armature spring 21 is so constructed that during its initial movement and before engaging the make contacts on the short arms 3 and 35 it will flex along its entire length in a large are from the point connected to its base. However, after the armature spring contacts engage the make contacts on the short arms 3t and 35, the armature spring 2! flexes most, if not entirely, near points 31 and 38 as the axis, due to the flexibility of the diverging portions forming the elongated slot 36, with respect to the flexibility of the short arms 34 and 35 thereby causing a longitudinal wiping action on a short are a compared to the length of the armature spring. The short arms 34 and 35 are also flexed, where they join with the main short portion dependent upon the movement of the armature spring, to wipe in short arcs of different lengths and in diiferent planes to produce a very efilcient wipin action in combination with the movement of the contacts on the armature spring.

Since the flexible arm 34 extends at right angles from the main stiff portion of spring 26, this arm is flexed in a short arc which is at right angles to the armature spring 2'! thereby causing its contact to wipe the cooperating armature contact on spring 21 at right angles, or in a lateral direction as compared to the longitudinal wiping action of the contact on the armature spring. In a similar manner the flexible arm 35, being L-shaped, obviously flexes in a short are which is oblique with respect to the wiping arc of the cooperating armature contact. Therefore, the contacts on the armature spring '21 wipe their cooperating contacts on the short arms at and 35 in a longitudinal arc while the contact on arm 34 wipes its cooperating armature contact in a lateral arc and the contact on arm 35 wipes its cooperating armature contact in an Oblique are thereby providing positive self-cleaning circuit contacts of low resistance. Even if one of the contacts on one of the diverging portions 3! or 38 engages its cooperating working contact on one of the short arms 34 or 35 of spring before the other contact does, the flexibility of the diverging portion 31 and 38 are such that the other diverging portion is additionally flexed to engage its associated contact on spring 25 while the first engaged portion is held by the tension of the engaged short arm, such as or 35. Therefore, due to the flexibility of the diverging portions 31 and 38 with respect to the somewhat stiffer flexibility of short arms 34 and 35, the contact pressure between the contacts are equalized when the armature spring is actuated. The wiping action in short arcs and in different planes in combination with the equalizing of contact pressure above described produces a very efficient and reliable diminutive relay for use in places where it is essential to keep the switching contacts clean and clear of dust and other particles which heretofore have at times prevented proper circuit closures.

It is well known that fast operating relays have what is known as contact-bounce or chattering of a switch spring due to being sharply struck by the operated armature spring or due to the release of the armature. When such a spring is struck by the armature spring it will momentarily vibrate creating openings and closings of the cooperating circuit contacts in accordance with the amplitude and vibratory frequency characteristics of the spring. Such amplitude and vibratory frequency depending upon the length and thickness since all the switch springs in a pile-up are made of the same metal. With springs of the same thickness, it is also known that the longer the spring, the longer the open period of each contact-bounce due to the lower vibratory frequency and larger amplitude and the shorter the spring, the shorter the open period of each contact-bounce due to the higher frequency and smaller amplitude. Even with relatively short springs it is difiicult to overcome contact-bounce, especially where fast and accurate circuit operations are required. The above principles apply also to twin contacts. customarily all twin" contacts either had a pair of contacts on each of two cooperating springs or a contact on each of a pair of arms formed from a single spring, but these pairs of arms were of equal length with the result that such arms, when struck, vibrated together at the same frequency and amplitude creating open contact riods at the same instant.

In applicants disclosure the arms 34 and 3-5 were purposely made short and of different length and shape to give them short vibratory periods and different vibratory frequencies and amplitildes when struck by the armature spring. Since the springs 34 and 35 are both short and are of different lengths and shape, they will vibrate at different frequencies and different amplitudes when struck. Even if contact-bounce should occur with this arrangement of short stiff then during a portion of each contact-bounce one of the contacts on one of the arms may be in engagement with its cooperating contact when the other contact on the other arm is dis from its cooperating contact. While there may be short periods in which both pairs of cooperating contacts are disengaged, nevertheless the open circuit period, during the contact-bounce" period, is materially reduced, because of the different amplitude and different frequency vibra tions of arms 34 and 35, to a negligible factor.

Having fully described the invention, what is considered to be new and desired to hav protected by Letters Patent is specifically pointed out in the following claims.

What is claimed is:

1. In. switching device comprising a. spring having a clamping base portion, a short stiff portion extending longitudinally from one end of said base portion, two independently flexible arms extending laterally from the free end of said short portion. a movable spring having a clamping base portion, and a long flexible arm extending first laterally from the side of said base portlon thereof and thereafter longitudinally, a pair of contacts on said long flexible arm in a line extending laterally across the longitudinally extending portion, one of said flexible arms of said first spring extending at an angle from said short stiff portion thereof and having a contact resistering with one of said pair of contacts, the other flexible arm of said first pring extending at an angle from the short stiff portion thereof and then longitudinally around the free end of the first flexible arm of said first spring and having a contact in the longitudinal portion thereof registering with the other contact of said pair, and means for moving said long flexible arm to cause the contacts on said long flexible arm to engage and move the contacts on said independently flexible arms in a wiping action, the said wiping action between said contact being in longitudinal, lateral and oblique planes to maintain said contacts clean and clear of dirt.

2. In a switching device comprising a movable spring, a stationary spring, means for clamping said springs in a. spring pile-up, said springs having main body portions extending from said clamping means in non-superposed relation thereby providing space to facilitate easy access for adjustments of said main body portions, parallel contact supporting branches on the main body portion of said movable spring, a contact on each of said contact supporting branches, said contacts spaced laterally acros the width of said movable sprin short arms of unequal length and shape extending from the free end of the main body portion of said stationary spring to positions in superposed relation with said contact supporting branches of said movable spring, a contact on each of said arm in alignment with the corresponding contacts on said contact supporting branches and engaged in response to the movement of said movable spring, and said contact supporting branches on said movable spring being independently flexible during movement of said movable spring and said short arms being independently flexible and having equal resistance to movement to thereby apply equal contact pressure to the cooperating pairs of contacts on said springs.

3. In a switching device spring pile-up com prising an armature spring having a base and a long flexible portion extending therefrom and movable in a path in a predetermined plane, a stationary spring having a base and a short still portion extending therefrom parallel to but out of the path of said predetermined plane, said portions being spaced apart and in offset relation to one side of each other to permit easy access for adjustment, short independently flexible arms of unequal length and different in shape having equal resistance to movement, extending from th free end of said short stiff portion into said predetermined plane in the path of said movable long flexible portion of said armature spring, a pair of contacts on said long flexible portion and cooperating contacts on said arms, means for moving said long flexible portion in said path in said predetermined plane to cause the contacts on said long flexible portion to engage and move the contacts on said arms, and a semi-rounded bushing secured to said long flexible portion for twisting at least a portion of said long flexible portion and the contacts thereon to equalize the contact pressure on said contacts in case one of said arms ofiers resistance to movement before the other arm.

FREDRIC E. WOOD. 

